Thermostatic switch



Oct. 9, y1923.-l

H. A. HOESCHEN THERMOSTATIC SWITCH Filed Jan. 3, 1921 2 Sheets-Sheet 1mw w m.

b'. A IOL'SCHEN.

Oct. 9, 1923.

H. A. HOESCHEN THERMOSTATIC SWITCH Filed Jan. is. 1921 2 Sheets-Sheet 22 l HA.H0ESCHEN.

@05M :IUMHW Patented Oct. 9, 1923.

lUNITED sTATas PATENT omer..

HENRY A. HOESCHEN, F OMAHA, NEBRASKA, ASSIGNOR 0F ONE-HALF TO BAKER ICEMACHINE COMPANY, 0F OMAHA, NEBRASKA,`A CORPORATION 0F NEBRASKA.

THERMOSTATIC SWITCH.

Application led January 3, 1921.

To all whom t may concern.'

` an electrical circuit or circuits in accordance with changes oftemperature.` It is the general object of my invention to provide athermostatic switch capable of direct ly opening and closing "electricalcircuits carrying currents of considerable amperage, and tothus enablethe auto-matic starting and stopping of motors large enough to oplcratecommercial refrigerating machines,

without the use of relays, or s'o-called automatic switches whichcontrol the motor circuits'and are controlled,in turn, by thermostaticswitches adapted only for use in circuits of low amperage. Moreparticular objects of my invention are to provide a switch having arelatively light and delicate member movable between opposed contactswhich are butslightly spaced there from, and which is held against oneor th-e' other of said opposed contacts by magnetic attraction so as tobe disengageable therefrom only by the application of such a force as tocause its immediate engagement with the opposed contact; and to providemeans for preventing arcing between the contacts when a circuit Visopened by the separation thereof. A further object of my invention is toprovide an electrical switch having a thermically actuated member ofmagnetic material which ismovable within a permanent magnetic field, andof which the contacts which are engaged to open and close the controlledelectrical circuits are in effect the poles of said permanent magneticfield. A further Object of my invention is lto provide in a switchhaving the characteristics last above mentioned lmea-ns for varying theintensity of the magnetic field, whereby to increase or decrease thetemp-erature-range within which the tliermically actuated member will beoperated. Further and more particular Serial No. 526,715.

objects of my invention will beset forth hereinafter.

In the accompanying drawings Fig. 1 is a longitudinal vertical sectionof a.device embodying my invention, portions thereof being broken awayto avoid undue extension ot the ligure, Fig. 2 is a front View of thedevice with the cover of the casing removed, Fig. 3 is a side view oftheentire device, a portion of the housing-tube being broken away to showthe enclosed thermo-sensitive member, Fig. t is a horizontal section onthe line 4 4 of Fig. 2, Fig. 5 is a detail vertical section of aslightly modified form of the device, showing the same as arranged forcontrolling two circuits, and Fig. 6 is a detail vertical section,showing a further .modification of the structure, wherein the contactsare immersed in oil.

In the illustrated embodiment of my invention the thermo-sensitivemember is a helical coil of metallic ribbon 6 formed by uniting stripsof two metals having different thermal expansibility, whereby relativerotational movements of t-he two ends of the coil are caused by veryslight changes of temperature, the movements being opposite in directionas the temperature increases and decreases. The endsof the coil 6 aresecured to the disks 7 and 8 and the lat-ter are fixedly connected,respectively, with the 'tubes 9 and 10, the former fitting rotatablywithin the latter and extending beyond the same at both ends.

For convenience in mounting the thermosensitive member in suitableproximity to the material of which the temperature is to be controlled,as for instance the'brine in a tank surrounding the expansion-coils of arefrigerating apparatus, and' at the same time to prevent injury to thesensitive member by direct contact therewith of the brine or othermaterial, the thermo-sensitive member is disposed within a tubularhousing 11 which is closed at the end adjoining vthe disk 7, and at theopposite end is fitted with a removable plug 12 through which the tubel() extends rotatably. The disk 8 has a projecting flange-portion whichengages the inner wall of the housing-tube and serves to su port thethermo-sensitive member in slightly spaced relation to the wall of thehousing. A threaded collar 13 is integrally united with the housing-tube11, as by welding the same thereon, said collar being adapted to belscrewed into a flange-plate 14 on the side of a brine-tank 15, so thatthe end of the housing containing the thermo-sensitive member willextendinto the tank, whilethe opposite end will project more or lessbeyond the side of the tank. The outer end of the housingtube isprovided with a flanged collar 16 to which is secured the switch-casingor hous ing 17, the latter being preferably of an impervious ormoisture-proof moldable insulating material such as bakelite. The casing17 is of oblong rectangular form, and at the front side has a removablecover 18, of which the central portion is preferably a plate 19 oftransparent glass or the like, through which the switch mechanism maylbe observed without opening the casing. The removable plug 12 at thefront end of the housing-tube 11 is preferably fiush with the rearinnersurface of the casing, the plug being retained by means of screws20 as shown in Fig. 2, so that by first removing said screws the parts6, 7, 8, 9, 10 and 12 may be withdrawn from the front end of fix:housing without disconnecting said parts from each other. The tube 10 isheld in fixed longitudinal relation to the plug 12 by means of a collar21 which is secured to said tube at the inner side of the plug, and anarm 22 which is secured upon the tube at the front side of the plugwithin the casing 17. A coil spring 23 is connected with the arm 22 andextends to a post 24 near one side of the casing, the tension of saidspring holding the upper portion of the arm against the end of anadjusting-screw 25 which extends through the side of the casing, as bestindicated in Fig. 2. The connecting tube 10, and the end of thethermo-sensitive member to which it is connected by the disk 8, are thusheld in fixed relation to the stationary parts of the device, subject toadjustment by means of the screw 25 which, when screwed inwardly of thecasing 17, rotates the tube 10 to the left or counter-clockwise asviewed in F ig. 2. The end of the tube 9, which projects forwardlybeyond the tube 10, is provided with an insulating sleeve 26 to which issecured the arm 27, the latter extendingsupwardly and carrying themovable members of the switch mechanism. The latter operate in amagnetic field formed between the termina-ls of a U-shaped perma- V nentmagnet 23. Said magnet is fixedly secured in the easing 17 by means ofscrews 29 which extend through the rear side of the casing and enterthreaded openings in theedges of the magnet, holdin the same against thelugs 30 and 31 which project from the back of the casing, so that themagnet is spaced from the rear wall thereof.

' The upper transversely extending lug 31 has lips 32 at the endsthereof which extend over the side-portions of the magnet, as

shown in Fig. 4, whereby to prevent spreading of the terminals or polesthereof, and a bar or rod 33 of non-magnetic material such as brass isarranged between the sides of the magnet adjacent to the lug 31, wherebyto positively'prevent any displacement of the poles toward each other.Near the ends of' the magnet, at opposite sides and in alinement witheach other, are threaded openings in which are disposed the screws 34and 35, said screws being of iron or soft steel so that adjacent endsthereof form pole-pieces for the magnet, and the strongest portion ofthe magnetic field is at the gap between said ends of the screws. Thescrew 34 extends through a package-sleeve 36 in the side of the casing17, so that said sz-rew may be turned from the outside of the casing,for adjusting the polar gap. Directly behind the screw 34 there is a s`rew 37 which passes through a second threaded opening in themagnet-terminal, the inner portion of said screw extending across towardthe opposite side of the magnet, and the outer portion of the screwextending outside the casing so that it may be adjusted without openingthe same. Said screw 37 is also of magnetic material and is employed4for varying the strength of the magnetic field between the ends of thescrews 34 and 35, it being obvious that a part of the magnetic forcewill be diverted or shunted to form a secondary field adjoining the endof said adjusting-screw 37, the intensity of the secondary field beinginversely proportional to the width of the airgap at the point of thescrew, and the intensity of the main field being decreased as that ofthe secondary field is increased. Below the screw 34'there is a screw 38which fits in a bushing 39 of insulating material vextending through theside of the magnet,

the outer or slotted end of the screw extending through a packing-sleevein they side of the casing 17, similarly to the screw 34. To the arm 27which is carried on the `front end of the tube 9 there is secured a flatstrip or bar 40 of magnetic material such as soft iron, which extends upbetween the ends of the screws 34 and 35, a thin plate 41 of insulatingmaterial being secured to one side of the bar adjoining the screw 35,whereby to prevent electrical Contact between said screw and the bar. Atthe opposite side of the bar 40 are two contact-springs 42 and 43, ofwhich the lower ends are attached to the arm 27, and the upper ends areadjacent, respectively, to the ends of the screws 34 and 33. Smallscrews 44 and 45 pass loosely through openings in the contact-springsnearv the free ends thereof and extend into threaded openings in the bar40. By means of said screws 44 and 45 the contact-springs are soadjusted that upon movement of the same away ,from the screws 34 and 38,the Contact will be first broken between the spring 42 1 and screw 34,and then between the spring 43 and screw 38. The screws 34 and 38 areelectrically connected to each other through a resistance 46,represented diagrammatically in Fig. 2. At the upper end of the casing17 are binding-posts 47 and l48, of which the first is connected withthe body of the magnet (and thus to the screw 34), and the other isconnected with the arm 27, as diagrammatically indicated, so that theswitch may be disposed in any electrical circuit by merely connectingtermina-ls thereof to the binding-posts. l

The described arrangement of contact and electrical connections issuitable for use with motors or other devices where the same are to becontrolled directly by the thermostatic switch. without theinterposition of relays, automatic electrically operated switches, orsimilar devices, and I have found it entirely practicable to operatemotors of sizes up to 5 horse-power with the motor-circuit connecteddirectly through the described switch mechanism, without causingappreciable arcing at the contacts, and without causing sticking,rheating or fusing thereof by continued use. The mode of operation ofthe mechanism will be apparent. The bar 40, being in effect an armature,tends to adhere or press firmly toward one or the other of the magnetpoles formed by the terminal portions of the screws 34 and 35,accordingto the direction in which the arm 27 is last actuated by thethermo-sensitive member. Upon a change of temperature suchas to tend toactuate the arm 27 in the opposite direction, the armature will continueto adhere to the engaged pole until the actuating force is suiiicient toovercome the magnetic attraction between the parts, whereupon thearmature will instantly move across the gap and engage the oppositepole, remaining in engagement therewith until the temperature is againincreased or decreased, as the case may be, suiciently tocause areversal of the movement. It should be noted that the arm 27 is notpositively actuated by the thermo-sensitive member 6, the coil of thelatter having a certain resilience which readily permits the deferredmovement of the switch-parts until the accumulation of the forcenecessary to effect a rapid movement thereof. When the controlledcircuit is closed by the engagement of the contact-springs 42 and 43with the terminal-screws 34 and 38, a firm and eilicient contact isformed between the parts and maintained constantly for the desiredperiod, without being subject to artial opening or chattering as aresult of jarring or vibration of the mechanism. The opening of thecircuit occurs only upon a full n'lovement of the parts, which israpidly s effected, since the samer is caused not only by theaccumulated force necessary to overcome the magnetic attraction of theengaged pole, but also by the counter attraction of the opposite pole,which becomes effective as soon as the movement is commenced. Thedescribed characteristics of the circuitopening movement tend to preventarcing between the contacts, and a further tendency to suppress arcingresults from the presence of the magnetic field, which tends in awellknown manner to inhibit the formation of an arc therein. Liabilityof arcing is further reduced by the use of the second or auxiliarycontact-screw 38 which is connected with the main contact-screw -34through tha resistance 46. As before mentioned, the rsprings 42 and 43are so adjusted that the connection is first broken between the spring42 and screw 34, thus throwing the resistance 46 into the circuit, whichremains closed momentarily, however, until the sepa ration of the spring43 and screw 38.

Referring now to Fig. 5, there is shown a modified arrangement of theswitch mechanism, adapted for use in connection with automatic switches,wherein the main switchy which opens and closes themotor-circuit 4isactuated by control-circuits connected through the thermostat, thelatter serving to close two control-'circuits alternately, eachcontrol-circuit being opened by the same action of the automatic switcheffected by the closing of said circuit at the thermostat, and the othercontrol-circuit being at the same time re-established at the automaticswitch so as to be closable by the reverse movement of the thermostat.In said modified structure the movable armature-bar 40 carries acontact-spring 42 at each side thereof, said springs being engageablewith contactscrews 34 which extend through insulating bushings 49 to theoutside of the casing 17. The bushings 49 extend through the tubularscrews or sleeves 50, which are of magnetic material such as iron orsteel and are screwed through the terminal portions of the magnet 28, sothat they constitute polepieces for the same and thus serve to attractthe armature-bar 4() and hold the contactsprings and screws in firmengagement with each other at one side or the other lof the polar gap.The arrangement of circuits with this form of the device is common andwell known in the art and need not be herein set forth in detail.

As a further means of preventing arcing 'between the switch-contacts,the same may be immersed in oil, which may be easily effected by thearrangement shown in Fig. 6. As indicated in said figure the magnet 28is inverted so that the ends thereof extend downwardly, and between saidends there is disposed a cup 5l of non-magnetic material such as brass,in which the oil is contained. The cup 51 is held in position by meansof lock-nuts 52 screwed upon the inner end-portions of the sleeves 50within the cup, suitable gaskets 53 being arranged between the nuts andthe sides of the cup to prevent leakage of the oil. In this form ot thedevice it is preferred that the end-portions of the contact-springs 42be slightly bent or turned outwardly adjoinin the ends of thecontact-screws 34', as by t is means 'it is possible to cause a slightrubbing or sliding of the contact-Surfaces upon each other as the samemove into and out of enga ement. i

ow, havin described my invention, what claim and esire to secure byLetters Patent is:

1. ln a device of the class described, the combination With athermically actuated membermovable reciprocatingly by increase anddecrease of temperatures, of an armature of magnetic material carried bysaid member, a permanent magnet having its poles extending on oppositesides of said armature whereby to attract the same alternatively,

a pair of yieldable contacts connected with said armature and havinportions extending into the magnetic fiel between the magnet poles, aair of fixed contacts engageable by said vie dable contacts in themagnetic field, and disengageable therefrom consecutively, and anelectrical resistance connecting said pair of fixed contacts.

2. In a device of the class described, a thermo-sensitive member, anarmature of magnetic materialconnected therewith and movable thereby inopposite directions ac-- cordin f to' increase and decrease oftemperature, a-shaped permanent magnet arranged with its poles atopposite sides of said armature whereby to attract the samealternatively, contacts controlled by said armature and adapted to openand close circuits at the limits of movement thereof, andmagnet-adjusting means for varying the intensity of the magnetic fieldin which the armature moves.

HENRY A. HOESCHEN.

